A rock-hard ridge of salt and sand more than two miles (three kilometers) long in Kenya's Chalbi Desert seemed like an illusion to photo assistant Alain Arnoux (flying in a motorized paraglider, above). "It's so straight, it looks man-made," says Arnoux. Such images of Africa—from pristine landscapes to severely degraded ones—are helping Mike Fay tell his story. "People must not only recognize they are stewards of our planet and all it contains," says Fay, "but that we now have the power to reverse existing environmental trends overnight."